Apparatus for air sterilization



Sept' 26, 1950 B. H. JENNINGs ErAL 2,523,373

APPARATUS FOR AIR STERILIZATION Filed May l0, 1946 2 Sheets-Sheet l Ey/2 /x v Li A A" n n n I A Alf l All n o n n 4n l|'\ n @2 u @n www e# m34/Www Sept. 26, 1950 B. H. JENNINGs ETAL 2,523,373

APPARATUS RoR AIR sTERILIzATIoN 2 sheetssneet' 2 Filed May 10, 1946 Patentecl Sept. 26, 1950 APPARATUS Fon Am s'rEBILIzA'rIoN Burgess H. Jennings and Edward Bigg,` Evanston, and Franklyn C. W. Olson, Wilmette, Ill., assignors, by mesne assignments, to Research Corporation, New York, N. Y., a corporation of New York Application M ay 10, 1946, Serial No. 668,948

This invention relates to the sterilization of air, and more particularly to the sterilization of air in places such as dormitories, hospitals, and auditoriums, Where people are exposed to cross infection by air-borne bacteria and viruses.

We use the term air sterilization as meaning the killing of air-borne bacteria, viruses, and molds, which invade the body through the respiratory tract. The problem of air sterilization is particularly acute in indoor public gathering places, hospitals, and living places for housing large numbers of people where, through opportunity for cross infection from one person to another, the'chances of infection of an individual are increased.

It has been found that introducing vapors of high boiling point polyhydroxy compounds into the air of an occupied space effects air sterilization. Vapors of triethylene glycol, propylene glycol, or ethylene glycol, are particularly elective. A concentration of triethylene glycol ranging from 0.003 to 0.005 milligram per liter of air (0.0013 to 0.0022 grain per -cubic foot) produces substantially instantaneous killing of bacteria sprayed into the air containing the triethylene glycol. Similar results are obtained with concentrations of 0.1 to 0.2 milligram per liter of air (0.044 to 0.088 grain per cubic foot) with propylene glycol. Optimum results are obtained if the humidity is 35% to 45%.

An obvious method of introducing and distributing glycol vapors in an enclosed space is to introduce the vapors into existing air conditioning, Ventilating, or heating ducts. However, this method has several objections. The variable conditions of temperature and humidity present in air conditioning, Ventilating, or heating ducts necessitated by changing weather affect the concentration of glycol vapors presen-t in the'duct. These variable conditions alter the amount of glycol vapor which can be held in air, thereby making it extremely difficult to maintain a substantially uniform glycol vapor concentration. If metal ducts are used, the problem of condensation of glycol on the metal presents itself. Glycol has a. high affinity for metal, and will condense thereon easily, particularly with a drop in temperature. Since high concentrations of glycol are required in a distribution duct for introducing glycol vapor intoan air space, condensation of 12 Claims. (Cl. 21-74) 2 glycol on metal surfaces in the duct results not only in ineiiicient operation, but also in dripping of the condensate upon the floor and furnishings of the space to be treated.

We avoid these objections by recirculating the air in the enclosed space, such as a dormitory room, at room temperature through a distribution system which inhibits vapor condensation therein, and introducing bactericidal vapors into the distribution system as ther air circulates therethrough. The bactericidal vapors (glycol vapors being assumed as an example) enter the distribution system at a temperature elevated above that of the air in the enclosed space, such as a dormitory room, so that there is no tendency for the glycol to condense as it enters the distribution system.

In practicing our invention, we utilize a nonmetallic means for conveying a mixture of vapor and air, such as a mixture of glycol vapor and air, of relatively high glycol vapor concentration to a plurality of outlets for securing uniform distribution of the mixture into the treated space. The problem of temperature change, which would tend to condense the glycol vapor, is overcome by .recirculating the air at room temperature or by pre-heating it prior to introducing it into the distribution system. A further factor in preventing glycol vapor condensation is the introduction of the glycol vapor into the distribution system at a point remote from metallic surfaces. In order to sterilize effectively the air in an enclosed space by using glycol vapors as the sterilizing medium and where glycol vapors are introduced into the air through a distribution system, it is desirable to have a, concentration of glycol vapors in the distribution system from 10 to 200 times the concentration desired in the treated space. To achieve this desired concentration, it is necessary to provide a distribution system which, when glycol vapors are introduced into it, will have a minimum condensing eect upon these vapors. Furthermore, it is necessary to control the temperature of the air passing through the distribution system and the temperature of the glycolvapor-air-mixture which is introduced into the distribution system in such a manner that condensation will be inhibited,

Accordingly, it is an object of this invention to provide a new and improved method and ap- Other objects of this invention are to provide a new and improved method and apparatus for maintaining a substantially constant predetermined concentration of bactericidal vapors in the air to be sterilized: to provide a. method and apparatus for sterilizing air in which the apparatus used is independent of existing air conditioning systems, and in which the rate of ilow of air through the apparatus, the air temperature, and humidity are controllable to maintain the bactericidal vapors introduced intosaid apparatus in vapor form; to provide a new and improved method and apparatus for sterilizing the air in an enclosed space by recirculating the air through a duct distribution system and introducing bactericidal vapors of substantially higher concentrations than the concentration desired in the treated space into the air passing through the duct distribution system. Y

These and other objects and advantages of our invention will become apparent from the following detailed description taken in conjunction with the attached drawings, in which Fig. 1 is a front elevational view showing a distribution duct with a blower and vaporizer attached thereto, the vaporizer being shown partly in cross section;

Fig. 2 is a diagrammatic showing of a room containing a distribution duct having a blower and vaporizer attached thereto;

Fig. 3 is a front elevational view, in cross section, of one form of vaporizer that can be used;

Fig. 4 is a front elevational view, in cross section, of another form of vaporizer that can be used; and

Fig. 5 is a front elevational view, in cross section, of still another form of vaporizer that can be used.

In Fig. 1, we have illustrated one embodiment of our invention in which a main distribution duct IU has attached thereto a blower assembly II for forcing air through the duct I0 and a vaporizer assembly I2 for introducing bactericidal vapors into the distribution duct III.

As is shown in Fig. 2, the distribution duct Ill normally extends the length of the space to be treated, such as a room I3, and contains a plurality of spaced outlets I4 for distributing bactericidal vapors into the air space of room I3. The air in room I3, or, if desired, outside air pre-heated to room temperature can be used, is drawn into the inlet opening, not shown, of

blower II, and is forced through the blower into ,When glycol vapors are used as the sterilizing medium, `and particularly if triethylene glycol vapors are used, we have found it desirable to use a treated asbesto-s duct, treated to be glycol resistant. As previously indicated, the main distribution duct I0 is connected to the discharge side of the blower II lat I6.

The vaporizer assembly `Il is Conneted t0 the f 4 distribution duct Il adjacent the discharge side of the blower II, as is shown in Fig. 1. This insures that the high concentration values of bactericidal vapors that are introduced into duct I0 are introduced as far as possible away from the metallic surfaces in the blower II.

The form of vaporizer illustrated in Figs. 1 and 3 includes a branch duct I'I joined to the main distribution duct Il at I8,.a second branch duct I9 joined to the main distributionA duct I0 at 20, and a connecting duct 2l connecting the two branch ducts I1 and I9. The branch ducts and connecting duct are conveniently housed in a housing 46, which also houses a source of bactericidal liquid 22 supported from the housing 46 by support member 23. In practice, the housing 46 can be made in compact closet form with a door which can be opened to permit ready inspection of the vaporizer assembly and to permit removal and replacement of f the bactericidal liquid source 22. The branch ducts I'I and I9 and connecting duct 2| are locatedvertically below the main distribution duct II). Likewise, the major portion of the housing 4B extends vertically `below the main distribution duct III, and the housing 46 is supported at the top. as indicated at 43 in Fig. l, by the main distribution duct I0. It will be observed that the branch ducts I1 and I9 and connecting duct 2I are in U-shape form.

Referring more particularly to Fig. 3, it will be noted that the branch duct I9 contains a. plurality of baiiies 24 which extend transversely of duct I9, and which are staggered with respect to each other. Baiiles 24 may be either of halfmoon shape, of segmental type, or perforated. The number of baiiles used will depend upon the maximum rate of evaporation desired. The individual baiiles extend more than half way across the diameter of duct I9 so as to cause a fluid medium, such as an air current, to traverse a tortuous path in moving throughv the duct. The baffles are arranged either horizontally or, .preferably, sloping downward slightly, so as to allow aliquid medium, such as a bactericidal liquid, to pass by the action of gravity -from one to the other, and also to prevent splashing or the admission of large drops or droplets of liquid into the main distribution duct l0. They are tted in such a manner that they may be removed easily for cleaning. The bales may be made of metal, which is treated to be corrosion resistant.

Bactericidal liquid, triethylene glycol being assumed as an example, is fed at a controlled rate into the upper part of duct I9 from a source 25. This feeding can be accomplished by gravity, pump, or any convenient means. As is shown in Fig. 3, it'is preferable to feed under the first baille 26 and onto the upper surface of the second baiiie 21. Feeding under the first baille 26 minimizes the opportunity for droplets of liquid to enter main distribution duct I0. The liquid passes from the top of one baille to the top of the next succeeding baille immediately below by the action of gravity until substantially all of the bales have liquid on their upper surfaces and liquid passing or dripping between these surfaces.

\A portion of the air passing through the main distribution duct I0 is diverted into duct I1 at point I8. This air passes through duct I1 and into duct 2 l, where, in turn, it passes over a plurality of heating elements 28, which raise the temperature of the air. The air then passes into duct I9, being aided by deflector plate 29, and winds past the ballies 24 before reentering the main distribution duct I at 2l.' The heated air in passing over the baille surfaces which contain bactericidal liquid, triethylene glycol being assumedl as an example, vaporizes the triethylene glycol, and the mixture of air and triethylene glycol vapors passes into duct II). To facilitate the reentry of the air into duct III, a venturi is provided, which creates a low pressure region adjacent the exit from duct I9. The low pressure point existing in the main distribution duct I0 adjacent the exit from-duct I3 at 20 not only facilitates the reentry of air into duct I0 at that point, but also creates\ a pressure differential,

which causes air to be diverted from the main .l

distribution duct I0 through ducts I`I,2I, and I9.

' noid valve 35 to cut off the supply of liquid to the baille members 24. In order to vary the amount of air which passes through vapprizer assembly I2, a rotatable damper 3B is provided.

Instead of diverting air from the main distribution duct I0 through the vaporizer assembly I2, a separate air feed could be' provided for the vaporizer. 'I'his is illustrated in Fig. 4 in which a separate fan means 31 forces air through a duct 38, over a heating element 39, and past a plurality of baille members 40. Otherwise, the operation of this vaporizer is the same as that illustrated in Fig. 3.

Another means to effect circulation of air past the baille members and into main distribution duct I0 is illustrated in Fig. 5. In the construction illustrated in this ligure, a chimney draft effect is obtained by positioning a heating coil 4I at the bottom of a columnar housing 42, which contains a plurality of staggered bailles 44 arranged in the manner previously described. Air

enters the bottom of the columnar housing 42v tericidal liquid, and pa'sses into the main dis" tribution duct. The mixture of vapors and air passes into the main distribution duct I0 in the manner previously described for the apparatus illustrated in Figs. 3 and 4. In all of these various modifications, it is preferable to introduce the mixture of bactericidal vapors and air into the main distribution duct at a low pressure point therein, such as is created by venturi 30.

When the bactericidal vapors enter the main distribution duct, they vare forced through the duct and out of the outlets I'4 by action of the blower assembly II. The distance between the outlets I4 is dependent upon the characteristics of the space to be treated. Preferably, the size of the outlets I4 is such that they have the chartake-03s may be installed to pipe the bactericidal vapors about the space to be treated.

As an example of the practice of our inventionl a satisfactory concentration of triethylene glycol vapors can be maintained in a dormitory of assumed proportions-say, feet long by 30 feet wide by 9 feet high, utilizing the following procedure and apparatus: A 6-inch glycol-resistant asbestos distribution duct extends substantially the length oi the dormitory adjacent the ceiling thereof. This duct contains openings spaced anywhere from 3 feet to 12 feet apart. Each opening is approximately 2 inches in diameter and has the characteristics' of an oriiice. The distribution duct is connected to a recirculating blower assembly, -which is controllable to move air through the distribution duct at a lrate of from 300 to 800 cubic ieet per minute at a static pressure oi' l8 inches Hg. A concentration of glycol vapors from l0 to A200 times the concentration desired in the treated space can be secured in the distribution duct by varying the amount of air which passes through the vaporizer assembly. The vaporizer assembly is attached to the main f distribution duct, and consists of asbestos ducts,

as is illustrated in Fig. 1. When the air passing through the" vaporizer contacts the baiiies, it is at a temperature of from 200 to 250 degrees F. The air which reenters the distribution duct as it is recirculated, and consequently which is introduced into the vaporizer, is at room temperature-say, from 55 to 80 degrees F. The complete cycle of operation, then, is that air enters the blower; passes through the blower; is discharged into the main distribution duct; a portion of the air is diverted into the vaporizer, is preheated, vaporizes the bactericidal liquid; the bactericidal vapors and air then reenter the main distribution duct, where they are forced along the duct and out of the outlets; vapors then disperse throughout the space to be treated; and the air in this space is then redrawn'into the blower.

It will thus be seen that. we have provided a method and apparatus for achieving sterilization of air in which the air is circulated and, while it is being circulated, bactericidal vapors are introduced into it in a lconcentration suiilciently high to maintain the concentration desired in the space being treated. Furthermore, maintenance of the desired concentration is furthered by minimizing possibilities of vapor condensation.

The apparatus which is used to accomplish this result is not complicated, is easy to install and maintain, and is eilicient in operation.

While we have described particular embodiments of our invention and the method of practicing said invention, we do not wish to be restricted thereto, but intend to cover all modications thereof which would be apparent to one skilled in the art and which come within the true spirit and scope of our invention.

We claim:

1. An air sterilization apparatus comprising'a distribution duct having a plurality of spaced outlets therein for distributing a mixture of air and bactericidal liquid vapors to the air in a space to be treated, a blower arrangement for forcing said mixture through said duct and out 0f said outlets, a U-shaped branch duct arrangement connected to the distribution duct adjacent the discharge side of said blower, each end of said U-shaped branch duct arrangement opening into the distribution duct, Ia construction in said distribution duct adjacent the end of said U-shaped branch duct arrangement farthest from the disl charge side of said blower whereby the pressure in the distribution duct'is reduced at this point i Y to vaporize bactericidal liquid therein whereby said air will contain bactericidal liquid vapors as it reenters the distribution duct.

2. An air sterilization apparatus comprising a distribution duct having a plurality of spaced outlets therein for distributing a mixture of air and bactericidal liquid vapors to the air in a space to be treated, means causing said mixture to ow through said duct and out of said outlets, a U- shaped branch duct arrangement connected to the distribution duct adjacent the discharge side of Said flow causing means said U-shaped branch duct arrangement extending vertically below said distribution duct and each end of said U-shaped branch duct arrangement opening into said distribution duct, a Venturi arrangementlocated in said distribution duct adjacent the opening therein forming the end of the branch of the U-shaped duct arrangement farthest from the discharge side of said flow causing means whereby the static pressure in said distribution duct is reduced at this point thereby causing a portion of the air passing through the distribution duct to pass through the U-shaped branch duct arrangement and reenter the distribution duct adjacent the Venturi arrangement, means for controlling the amount'of air passing through said U-shaped branch duct arrangement, and means for causing said air to vaporize bactericidal liquid v contained within said U-shaped branch duct arrangement whereby said air contains bactericidal vapors as it reenters the distribution duct.

3. An apparatus for introducing bactericidal liquid vapors into the air of an enclosed space comprising a substantially horizontal distribution duct for distributing a mixture of said vapors and air to the air in the enclosed space, a blower arrangement for forcing said mixture through said duct, a U-shaped branch duct arrangement connected to and extending vertically downward from said distribution duct Vadjacent the discharge side of said blower, each end of said U- shaped branch duct arrangement opening into the distribution duct, means for diverting a portion of the air passing through the distribution duct through said U-shaped branch duct arrangement, means for heating said diverted air and means for bringing said heated diverted air into contact with a plurality of bactericidal liquid containing surfaces to cause liquid on said surfaces to be vaporized whereby the air reentering the distribution duct contains bactericidal liquid vapors.

4.' An apparatus for introducing triethylene glycol vapors into the air in an enclosed space comprising a distribution duct for distributing a mixture of air and triethylene glycol vapors into the air in said enclosed space, a blower arrangement for forcing said mixture through said duct and into the air in said space, means for diverting a portion of the air passing through said distribution duct through a U-shaped branch duct arrangement and back into said distribution duct, means for lheating said diverted air to a temperature suflicient to cause vaporization of the triethylene glycol liquid, and means for bringing said heated air into contact with the triethylene glycol liquid wherebythe air reentering the distribution duct contains triethylene glycol vapors.

5. Anapparatus for recirculating the air within an enclosed space and for continuously introducing into said air during recirculation thereof vapors of triethylene glycol comprising an asbestos distribution duct having a blower connected thereto, a U-shaped branch asbestos duct arrangement connected to said distribution duct adjacent the discharge side of said blower, each end of said U-shaped branch asbestos duct arrangement opening into said distribution duct, means for diverting a portion of the air passing through said distribution duct through said U- shaped branch asbestos duct arrangement, means for heating said diverted air to a temperature of from 200 F. to 250 F., a plurality of transverse bailles located within a branch of said U-shaped asbestos duct arrangement, said bailles having triethylene glycol liquid on individua1 surfaces thereof, and means to bring said heated air into contact with said baille surfaces whereby the triethylene glycol liquid is vaporized and the air reentering the main distribution duct contains triethylene vapors.

6. In an apparatus for effecting sterilization of the air in an enclosed space having means for recirculating the air in saidspace and means for introducing bactericidal liquid vapors into said air as it is recirculated, a vaporizer comprising a columnar housing, a `plurality of bailles located within said housing and extending transversely of the longitudinal axisthereof, said baiiles being staggered with respect to each other and each individual baille blocking off more than half of the diameler of said columnar housing, means to feed .bactericidal liquid onto the upper surfaces of said bailles, means to collect excess liquid fed to said bailles, a source of air, means to heat said air, means to force said air past said bales, and means to discontinue said liquid feed to said bailles upon failure of air ow past said baffles.

7. In an apparatus forl effecting sterilization of the air in an enclosed space having means for recirculating the air in said space and means for introducing bactericidal liquid vapors intor said air as it is recirculated, a vaporizer comprising a columnar housing, a plurality of bailies located in said columnar housing and disposed transversely 'of the longitudinal axis thereof, said baflles being staggered with respect to each other, means to feed bactericidal liquid onto the upper surfaces of said baffles, said liquid feeding means being located adjacent the top of said columnar housing, means to cause air to ow past said bailles, means to heat said air prior to contact with said bailles, and means to control the amount of air flowing past said baffles.

8. In apparatus for introducing lbactericidal vapors into the air of an enclosed space comprising a main duct having an outlet communieating vwith said enclosed space, a blower for moving air through said main duct, a branch duct communicating with said main duct bev tween said blower and outlet, a columnar vaporbactericidal liquid to the upper surfaces of -said baies in the vaporizing chamber for vaporization therein.

9. The apparatus as set forth in claim 8 together with means for controlling the rate4 of vaporization of said bactericidal liquid in said vaporizing chamber.

10. The apparatus as set forth in claim 8 in which the vaporizing chamber, that portion of the branch duct between the vaporizing chamber and the main duct, and all of the main duct extending from the point of entry of the branch duct to said outlet have a non-metallic inner surface.

11. The apparatus as set forth in claim 8 in which a Venturi device is built into the main duct at the point of entry of the branch duct, whereby the movement of air through the main duct induces a flow of air through said branch duct.

10 12. 'I'he apparatus as set forth in claim 8 in which the bactericidal liquid is triethylene glycol, and the air in the vaporizing chamber is heated to a temperature of from 200 to 250 F.

BURGESS H. JENNINGS.

EDWARD BIGG.

FRANKLYN C. W. OLSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,150,263 Chesney Mar. 14, 1939 2,209,775 Karlsteen July 30, 1940 2,268,769 Newton Jan. 6, 1942 2,313,976 Sullivan Mar. 16, 1943 2,344,536 Coey et al. Mar. 21, 1944 2,369,900 Jennings et al. Feb. 20, 1945 Certificate of Correction September 26, 1950 Patent No. 2,523,373

BURGESS H. JENNINGS ET AL.

erroroppeers in the printed speeioation of the above It is hereby certied that orrection as follows:

numbered patent requiring o Column 6, line 74, for the Word eonstruetion read constriction;

and that the seid Letters Patent should be read as corrected above, so that the same may conform to the record of the oase in the Patent Oce.

Signed and sealed this `5th day of December, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

